The draft sequence of the human genome was published in 2001 by the Human Genome Consortium (Nature Vol 409; issue 6822) and Celera Genomics (Science, Vol 291, issue 5507, 1304-1351). Capitalizing on this investment and realizing the potential of the Human Genome Project requires a better understanding of genetic variation and its effect in disease.
It has been estimated that any two copies of the human genome differ from one another by as little as 0.1%—in other words, a total of three million variants, or one variant every 1000 bases over a total of three billion that make up the human genome. Since such variation can affect disease susceptibility and responses to drugs, it is essential to identify the genetic factors which contribute to biological variation. DNA sequencing is a fundamental tool enabling the screening of genes for such genetic mutations associated with disease. High throughput and high accuracy sequencing methods are therefore required to screen the complete genome sequence of an animal in order to identify unique nucleic acid sequences, which may indicate the presence of or predisposition to various physiological or pathological conditions.
DNA sequencing of large and complex genomes is currently limited by cost. With a significant proportion of human genomic DNA comprising repetitive sequences, reducing the sequence complexity of the sample of genomic DNA reduces the amount of sequencing required. Furthermore, with prior genetic information, it is possible to correlate a phenotype, such as a predisposition to a disease, with the genetic variation of one or more regions of the genome. What is desired is the application and advantages of high throughput sequencing methods specifically to these regions of interest among many individuals. In addition, in certain circumstances, it is desirable to generate a ‘genome-wide’ analysis of a particular genomic feature, such as an exon, to correlate genetic diversity in the protein-coding regions across many individuals.
Consequently, there is a need for targeted sequencing of gene-rich regions that can provide an alternative approach to whole genome sequencing.